| dc.description.abstract | The primary goal of this study was to examine the physical and biological structure of
riparian zones along streams in the Boreal forest of Northwestern Ontario and to discover
whether riparian structure was related to key hydrologic variables, including watershed
area and surficial geology. The first objective was to verify the relationship between
watershed area and physical and hydrological stream characteristics including discharge,
temperature, and gradient. The second objective was to determine the variability in
stream characteristics within a watershed scale based on differences in physical and
hydrological drainage basin characteristics. The third objective was to describe the
differences in the vegetation communities in riparian zones and upland communities.
The fourth objective of the study examined riparian structure and composition along
streams within watersheds that differ in physical and hydrological characteristics. The
Mackenzie, Wolf, and Spruce River watersheds were used in a nested sampling design
with watershed area class as a grouping variable. A total of 40 streams were sampled
having approximately 1 (n = 12), 10 (n = 12), 40 (n = 8) and 100 (n = 8) km2 watersheds.
Stream discharge, temperature and gradient, and riparian width and slope were measured
while surficial geology was evaluated. Riparian and upland plots were sampled on both
sides of the stream and vegetation species were recorded. The results showed clear
relationships among physical and hydrological stream and drainage basin characteristics
and riparian vegetation structure. As drainage area increased, stream discharge and
temperature increased and stream gradient decreased. Stream temperature and gradient
were lowest in streams with meadow marsh riparian zones. Riparian width decreased
while riparian slope increased with increases in drainage area. Riparian width was
greatest, and riparian slope least in meadow marsh riparian zones, while the width was
narrowest and slope greatest in conifer swamp riparian zones. Streams with both 1 and
10 km2 watersheds had riparian zones which had lower vegetation species diversity than
the surrounding upland timber zone. A discriminant function analysis revealed Speckled
Alder, Aspen, and Beaked Hazel characterizing the riparian zones of smaller streams (1
km2 watershed), grasses and sedges characterizing the riparian zones of intermediate
sized streams (10 km2 watershed), and Cedar, Honeysuckle and Currants characterizing
riparian zones around large streams (100 km2 watersheds). There was a positive
relationship between drainage area and the drainage basin’s surface roughness,
width/depth ratio, and stream channel sinuosity, while there was a negative relationship
between drainage area and the drainage basin’s stream channel and basin slopes. This
study characterized riparian vegetation structure along a stream continuum to understand
better the structure and function of riparian communities and will be used as part of a first
step towards assessing the possible effects of timber harvesting on aquatic ecosystems to
ensure the effective management of riparian forest ecosystems. | |
